Mobile devices are carried by a user throughout most or all of a day. During the day, the user may encounter many different environments, each with a different background noise characteristic and other acoustic effects. Mobile devices employ noise cancelling to take into account the environmental changes and improve the user's experience while using the mobile device. However, the performance of noise cancelling systems vary with how closely a speaker of the mobile device is placed against the user's ear, because the coupling between the user's ear and the speaker varies with distance.